Adaptive-noise canceling (ANC) effectiveness estimation and correction in a personal audio device

摘要

Techniques for estimating adaptive noise canceling (ANC) performance in a personal audio device, such as a wireless telephone, provide robustness of operation by triggering corrective action when ANC performance is low, and/or by saving a state of the ANC system when ANC performance is high. An anti-noise signal is generated from a reference microphone signal and is provided to an output transducer along with program audio. A measure of ANC gain is determined by computing a ratio of a first indication of magnitude of an error microphone signal that provides a measure of the ambient sounds and program audio heard by the listener including the effects of the anti-noise, to a second indication of magnitude of the error microphone signal without the effects of the anti-noise. The ratio can be determined for different frequency bands in order to determine whether particular adaptive filters are trained properly.

主权项

1. A personal audio device, comprising:
a personal audio device housing; a transducer mounted on the housing for reproducing an audio signal including both source audio for playback to a listener and an anti-noise signal for countering effects of ambient audio sounds in an acoustic output of the transducer; a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds; an error microphone mounted on the housing in proximity to the transducer for providing an error microphone signal indicative of the acoustic output of the transducer and the ambient audio sounds at the transducer; and a processing circuit that adaptively generates the anti-noise signal from the reference signal by adapting a first adaptive filter to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal and the reference microphone signal, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the source audio and a combiner that removes the source audio from the error microphone signal to provide the error signal, wherein the processing circuit computes a ratio of a first indication of a magnitude of the error microphone signal including effects of the anti-noise signal to a second indication of the magnitude of the error microphone signal not including the effects of the anti-noise signal to determine an adaptive noise canceling gain, wherein the processing circuit compares the adaptive noise cancelling gain to a threshold gain value, wherein the processing circuit takes action on the anti-noise signal in response to determining that the adaptive noise canceling gain is greater than the threshold gain value, wherein the processing circuit filters the error signal with a first low-pass filter to generate the first indication of the magnitude of the error microphone signal, and wherein the processing circuit filters the reference microphone signal with a second low-pass filter to generate the second indication of the magnitude of the error microphone signal.